. >>> the latest quinnipiac university "new york times" cbs news poll shows obama leading in ohio, florida and pennsylvania. it matches our own marist polling which shows the president leading in all nine swing states. joining me now, peter brown, the assistant director of the quinnipiac university polling institute. peter, i want to ask you about historically speaking have the polls been largely accurate? >> yes. the polls have been quite accurate over time. now, everybody likes to point to the 1948 election when the polls said that thomas dewey would win the election and he didn't. harry truman did. that was 40 years ago when polling was in its infancy. polls are very good at telling you what the situation is at the time they're taken, not a week from thursday, not two months from tomorrow. they're good for then. >> that snapshot, right. some of the gop complain the pollsters are oversampling democrats in the swing states. are they overestimating democratic turnout for november? can you explain how this works? >> sure. the key is that we and most of the other major polls do not weight by